Nowadays a great variety of progressive addition lenses are designed and marketed by a great number of spectacle lens manufacturers. Among these progressive addition lenses, balance type progressive addition lenses with so-called “balance type design” are most highly demanded, and therefore widely sold and widely used. Such balance type progressive addition lenses are designed so as to have a wide distance vision area, and an intermediate-to-near vision area wide enough for general use. Most of the balance type progressive addition lenses marketed by the great number of spectacle lens manufacturers are designed so as to be able to be easily worn by any user in any situation.
However, even with the progressive addition lens with balance type design, there are still many cases where the user is dissatisfied with the vision that he (or she) has seen through the lenses of the completed spectacles. First, the content of the dissatisfaction with the progressive addition lens with balance type design includes dissatisfaction with the width of the clearly viewable vision when viewing distant objects and the width of the clearly viewable vision when viewing near objects through the lens.
On the other hand, due to progressive change of the power from the distance vision area to the near vision area of the progressive addition lens, distortion and blurring of image in the lateral portion ranging from the intermediate vision area to the near vision area of the lens are caused. Due to the distortion and blurring, when fluctuation of image caused while the user moves his (or her) line-of-sight becomes large, the user will be dissatisfied with unnatural vision he (or she) has seen caused by the fluctuation of image. It is known that the aforesaid two dissatisfactions are the main dissatisfactions when using the progressive addition lens.
The aforesaid two dissatisfactions are antithetical to each other, and it is impossible to reduce the two dissatisfactions at the same time. For example, the relation of the two dissatisfactions is: if trying to design a progressive addition lens to further widen the clearly viewable vision when viewing distant objects and the clearly viewable vision when viewing near objects through the lens, the distortion and blurring of image in the lateral portion and the fluctuation of image caused while the user moves his (or her) line-of-sight will become larger. Thus, it is impossible to reduce the two dissatisfactions at the same time. Further, even if the user does not particularly express dissatisfaction, it does not necessarily mean that the user is quite satisfied with the progressive addition lens.
Although there are progressive addition lenses exclusively designed to meet the specific use requirements such as reading, doing desk work, operating personal computer, playing sports (such as golf and tennis) and the like, these progressive addition lenses have defects when being used for other purposes than the use requirements they are designed to meet. For example, a progressive addition lens for the purpose of reading and desk work is designed to have a wider near vision area. Thus, the distortion and blurring of image in the lateral portion ranging from the intermediate vision area to the near vision area of the lens are increased, and the fluctuation of image caused when the user moves his (or her) line-of-sight is increased. Further, since the clearly viewable vision of the distance vision area is narrow, it will be inconvenient to use the spectacles with such progressive addition lenses when going outside, although it can be comfortably used to read and do desk work in the room. In other words, since the distance vision area of the lens is narrow, it is difficult to have a wide view of distant objects. Further, as described above, since the distortion and blurring of image in the lateral portion ranging from the intermediate vision area to the near vision area of the lens and the fluctuation of image caused when the user moves his (or her) line-of-sight are large, the distortion, blurring and fluctuation of image will become serious especially when the user is moving.
While a progressive addition lens for the purpose of playing outdoor sports such as golf, tennis and the like is designed to have a wider distance vision area, so that the distortion and blurring of image in the lateral portion ranging from the intermediate vision area to the near vision area of the lens and the fluctuation of image caused when the user moves his (or her) line-of-sight are reduced. The clearly viewable vision ranging from the intermediate vision area to the near vision area is narrowed, so that such progressive addition lens can be comfortably used when playing outdoor sports. On the other hand, the defect of the spectacles with such progressive addition lenses is that the near vision area is narrow when using such spectacles to read books and newspapers, or do desk work.
As described above, the progressive addition lens exclusively designed to meet the specific use requirements is difficult to be used for wide purposes, and therefore such lens is used for alternative uses.
On the other hand, unlike the progressive addition lens exclusively designed to meet the specific use requirements such as reading, doing desk work, operating personal computer, and playing sports (such as golf and tennis and the like), the aforesaid progressive addition lens with balance type design is limited in its performance for each individual use, and is inferior to the exclusively designed progressive addition lens in each individual use. However, the balance type lens is a progressive addition lens capable of being used somewhat comfortably for wide purposes, and is widely demanded and widely sold. Thus, the issue for the lens manufacturers is to relieve dissatisfactions of each individual user with the balance type progressive addition lens as much as possible, and develop a balance type progressive addition lens satisfied by the user more than ever before.
To tackle this issue, there is disclosed a technique for providing a progressive addition lens with a design most suitable for each individual user from a plurality of previously prepared progressive addition lenses with different designs (see Patent Document 1).
This technique is developed to select a lens for each individual user from a plurality of progressive addition lens types based on information such as user's age and wearing environment so that the selected lens is most suitable for the user, wherein the plurality of progressive addition lens types are each previously assigned to evaluation data such as user's age and suitability for his (or her) career and hobby (as wearing environment and the like). Here, the wearing environment and the like of the user represents information such as whether the user mostly uses the lens to do outdoor activities, or the user mostly uses the lens to de indoor activities, or the user does not particularly mostly uses the lens to do outdoor activities or indoor activities in association with his (or her) career and hobby, and whether the user has experience of using a progressive addition lens.
Similarly, there is disclosed another technique for providing a progressive addition lens with a design most suitable for each individual user from a plurality of prepared progressive addition lenses each with different designs (see Patent Document 2).
This technique is developed to acquire detail individual information of each individual user, and design and manufacture a progressive addition lens optimally customized for the user based on the acquired individual information. In such technique, dozens or more basic parameters are prepared, wherein the basic parameters each determines the area of distinct vision of both the distance portion and the near portion, which are bases of the design of the progressive addition lens. As a method for determining one basic parameter from the prepared basic parameters, a first basic parameter based on user's career is selected, further, a second basic parameter based on user's hobby is selected, and thereby basic parameters of the progressive addition lens suitable for the user are selected.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. H03-206417    [Patent Document 2] Patent application publication WO 98/16862